no sound from my laptop

I have a Hp pavillion DV9608 and Windows Vista home premium. Recently the speakers have stopped working. The taskbar says "NO audio output device is installed" and is x ed out. My device manager says no audio device installed. I downloaded the latest Conexant driver and it still doesn,t work. The last time this happened I did a system restore and I had sound for awhile but again it has stopped working. This seems like a very commmon problem with these laptops, is it a problem with the sound card, drivers or operating system. Please help, so I dont have to junk this laptop and by something else.